The Son of Neptune (Book 2)

Percy is confused. When he awoke from his long sleep, he didn't know much more than his name. His brain fuzz is lingering, even after the wolf Lupa told him he is a demigod and trained him to fight with the pen/sword in his pocket. Some how Percy manages to make it to a camp for half-bloods, dispite the fact that he has to keep killing monsters along the way. But the camp doesn't ring any bells with him. The only thing he can recall from his past is another name: Annabeth.